osfs: Add new BoundOS type

Create the new BoundOS osfs type, which works as a
pass-through filesystem for files descending from base dir.

For backwards compatibility the previous behaviour is
still the default and is now represented by the ChrootOS
type.

Signed-off-by: Paulo Gomes <pjbgf@linux.com>

go.mod

@@ -3,12 +3,20 @@ module github.com/go-git/go-billy/v5
 // go-git supports the last 3 stable Go versions.
 go 1.19
 
+replace github.com/cyphar/filepath-securejoin => github.com/pjbgf/filepath-securejoin v0.0.0-20230821001828-0ca74e6d4bf8
+
 require (
-	golang.org/x/sys v0.8.0
+	github.com/cyphar/filepath-securejoin v0.2.3
+	github.com/onsi/gomega v1.27.10
+	golang.org/x/sys v0.11.0
 	gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c
 )
 
 require (
+	github.com/google/go-cmp v0.5.9 // indirect
 	github.com/kr/pretty v0.2.1 // indirect
 	github.com/kr/text v0.2.0 // indirect
+	golang.org/x/net v0.12.0 // indirect
+	golang.org/x/text v0.11.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -1,11 +1,29 @@
 github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
+github.com/go-logr/logr v1.2.4 h1:g01GSCwiDw2xSZfjJ2/T9M+S6pFdcNtFYsp+Y43HYDQ=
+github.com/go-task/slim-sprig v0.0.0-20230315185526-52ccab3ef572 h1:tfuBGBXKqDEevZMzYi5KSi8KkcZtzBcTgAUUtapy0OI=
+github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
+github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+github.com/google/pprof v0.0.0-20210407192527-94a9f03dee38 h1:yAJXTCF9TqKcTiHJAE8dj7HMvPfh66eeA2JYW7eFpSE=
 github.com/kr/pretty v0.2.1 h1:Fmg33tUaq4/8ym9TJN1x7sLJnHVwhP33CNkpYV/7rwI=
 github.com/kr/pretty v0.2.1/go.mod h1:ipq/a2n7PKx3OHsz4KJII5eveXtPO4qwEXGdVfWzfnI=
 github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
 github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
-golang.org/x/sys v0.8.0 h1:EBmGv8NaZBZTWvrbjNoL6HVt+IVy3QDQpJs7VRIw3tU=
-golang.org/x/sys v0.8.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+github.com/onsi/ginkgo/v2 v2.11.0 h1:WgqUCUt/lT6yXoQ8Wef0fsNn5cAuMK7+KT9UFRz2tcU=
+github.com/onsi/gomega v1.27.10 h1:naR28SdDFlqrG6kScpT8VWpu1xWY5nJRCF3XaYyBjhI=
+github.com/onsi/gomega v1.27.10/go.mod h1:RsS8tutOdbdgzbPtzzATp12yT7kM5I5aElG3evPbQ0M=
+github.com/pjbgf/filepath-securejoin v0.0.0-20230821001828-0ca74e6d4bf8 h1:nqjCeQ2TVnccihhBoVBd0p+70hCFT4yqJKhfc8l1D50=
+github.com/pjbgf/filepath-securejoin v0.0.0-20230821001828-0ca74e6d4bf8/go.mod h1:aPGpWjXOXUn2NCNjFvBE6aRxGGx79pTxQpKOJNYHHl4=
+golang.org/x/net v0.12.0 h1:cfawfvKITfUsFCeJIHJrbSxpeu/E81khclypR0GVT50=
+golang.org/x/net v0.12.0/go.mod h1:zEVYFnQC7m/vmpQFELhcD1EWkZlX69l4oqgmer6hfKA=
+golang.org/x/sys v0.11.0 h1:eG7RXZHdqOJ1i+0lgLgCpSXAp6M3LYlAo6osgSi0xOM=
+golang.org/x/sys v0.11.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/text v0.11.0 h1:LAntKIrcmeSKERyiOh0XMV39LXS8IE9UL2yP7+f5ij4=
+golang.org/x/text v0.11.0/go.mod h1:TvPlkZtksWOMsz7fbANvkp4WM8x/WCo/om8BMLbz+aE=
+golang.org/x/tools v0.9.3 h1:Gn1I8+64MsuTb/HpH+LmQtNas23LhUVr3rYZ0eKuaMM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

osfs/os.go

@@ -1,140 +1,101 @@
+//go:build !js
 // +build !js
 
 // Package osfs provides a billy filesystem for the OS.
-package osfs // import "github.com/go-git/go-billy/v5/osfs"
+package osfs
 
 import (
-	"io/ioutil"
+	"fmt"
+	"io/fs"
 	"os"
-	"path/filepath"
 	"sync"
 
 	"github.com/go-git/go-billy/v5"
-	"github.com/go-git/go-billy/v5/helper/chroot"
 )
 
 const (
-	defaultDirectoryMode = 0755
-	defaultCreateMode    = 0666
+	defaultDirectoryMode = 0o755
+	defaultCreateMode    = 0o666
 )
 
-// Default Filesystem representing the root of the os filesystem.
-var Default = &OS{}
-
-// OS is a filesystem based on the os filesystem.
-type OS struct{}
-
 // New returns a new OS filesystem.
-func New(baseDir string) billy.Filesystem {
-	return chroot.New(Default, baseDir)
-}
-
-func (fs *OS) Create(filename string) (billy.File, error) {
-	return fs.OpenFile(filename, os.O_RDWR|os.O_CREATE|os.O_TRUNC, defaultCreateMode)
-}
-
-func (fs *OS) OpenFile(filename string, flag int, perm os.FileMode) (billy.File, error) {
-	if flag&os.O_CREATE != 0 {
-		if err := fs.createDir(filename); err != nil {
-			return nil, err
-		}
-	}
-
-	f, err := os.OpenFile(filename, flag, perm)
-	if err != nil {
-		return nil, err
+func New(baseDir string, opts ...Option) billy.Filesystem {
+	o := &options{}
+	for _, opt := range opts {
+		opt(o)
 	}
-	return &file{File: f}, err
-}
 
-func (fs *OS) createDir(fullpath string) error {
-	dir := filepath.Dir(fullpath)
-	if dir != "." {
-		if err := os.MkdirAll(dir, defaultDirectoryMode); err != nil {
-			return err
-		}
+	if o.Type == BoundOSFS {
+		return newBoundOS(baseDir)
 	}
 
-	return nil
+	return newChrootOS(baseDir)
 }
 
-func (fs *OS) ReadDir(path string) ([]os.FileInfo, error) {
-	l, err := ioutil.ReadDir(path)
-	if err != nil {
-		return nil, err
-	}
-
-	var s = make([]os.FileInfo, len(l))
-	for i, f := range l {
-		s[i] = f
+// WithBoundOS returns the option of using a Bound filesystem OS.
+func WithBoundOS() Option {
+	return func(o *options) {
+		o.Type = BoundOSFS
 	}
-
-	return s, nil
 }
 
-func (fs *OS) Rename(from, to string) error {
-	if err := fs.createDir(to); err != nil {
-		return err
+// WithChrootOS returns the option of using a Chroot filesystem OS.
+func WithChrootOS() Option {
+	return func(o *options) {
+		o.Type = ChrootOSFS
 	}
-
-	return rename(from, to)
-}
-
-func (fs *OS) MkdirAll(path string, perm os.FileMode) error {
-	return os.MkdirAll(path, defaultDirectoryMode)
 }
 
-func (fs *OS) Open(filename string) (billy.File, error) {
-	return fs.OpenFile(filename, os.O_RDONLY, 0)
+type options struct {
+	Type
 }
 
-func (fs *OS) Stat(filename string) (os.FileInfo, error) {
-	return os.Stat(filename)
-}
+type Type int
 
-func (fs *OS) Remove(filename string) error {
-	return os.Remove(filename)
-}
+const (
+	ChrootOSFS Type = iota
+	BoundOSFS
+)
 
-func (fs *OS) TempFile(dir, prefix string) (billy.File, error) {
-	if err := fs.createDir(dir + string(os.PathSeparator)); err != nil {
+func readDir(dir string) ([]os.FileInfo, error) {
+	entries, err := os.ReadDir(dir)
+	if err != nil {
 		return nil, err
 	}
+	infos := make([]fs.FileInfo, 0, len(entries))
+	for _, entry := range entries {
+		fi, err := entry.Info()
+		if err != nil {
+			return nil, err
+		}
+		infos = append(infos, fi)
+	}
+	return infos, nil
+}
 
-	f, err := ioutil.TempFile(dir, prefix)
+func tempFile(dir, prefix string) (billy.File, error) {
+	f, err := os.CreateTemp(dir, prefix)
 	if err != nil {
 		return nil, err
 	}
 	return &file{File: f}, nil
 }
 
-func (fs *OS) Join(elem ...string) string {
-	return filepath.Join(elem...)
-}
-
-func (fs *OS) RemoveAll(path string) error {
-	return os.RemoveAll(filepath.Clean(path))
-}
-
-func (fs *OS) Lstat(filename string) (os.FileInfo, error) {
-	return os.Lstat(filepath.Clean(filename))
-}
-
-func (fs *OS) Symlink(target, link string) error {
-	if err := fs.createDir(link); err != nil {
-		return err
+func openFile(fn string, flag int, perm os.FileMode, createDir func(string) error) (billy.File, error) {
+	if flag&os.O_CREATE != 0 {
+		if createDir == nil {
+			return nil, fmt.Errorf("createDir func cannot be nil")
+		}
+		if err := createDir(fn); err != nil {
+			return nil, err
+		}
 	}
 
-	return os.Symlink(target, link)
-}
-
-func (fs *OS) Readlink(link string) (string, error) {
-	return os.Readlink(link)
-}
-
-// Capabilities implements the Capable interface.
-func (fs *OS) Capabilities() billy.Capability {
-	return billy.DefaultCapabilities
+	f, err := os.OpenFile(fn, flag, perm)
+	if err != nil {
+		return nil, err
+	}
+	return &file{File: f}, err
 }
 
 // file is a wrapper for an os.File which adds support for file locking.